Fungal infections associated with the nails of the hands and feet are difficult to treat, particularly in the later stages of the disease. Infections associated with the nails of the feet and hands include onychomycosis, the fungal infection tinea pedis (athlete's foot), and the bacterial infection paronychia, a superficial infection of the skin caused by staphylococci and yeast. However, particularly difficult to treat is onychomycosis.
Onychomycosis is a fungal infection which can spread beneath and over the fingernails and toenails and the nail beds located under the nails. Nails infected with onychomycosis often become thickened and lusterless with debris accumulating beneath the free edge of the nail. Onychomycosis and similar infections have become more common and more intractable in recent years particularly in immunosuppressed patients, such as patients infected with Human Immunodeficiency Virus (HIV) or patients suffering from Acquired Immunodeficiency Syndrome (AIDS).
Even in otherwise healthy patients, onychomycosis is difficult to treat, particularly in its later stages. For example, most skin infections and dermatological conditions respond very well to topical antifungal preparations such as the imidazole derivatives (miconazole, clotrimazole, enconazole, ketoconazole) described in U.S. Pat. No. 3,717,655, as useful for the topical treatment of fungal infections. Other topical treatments, such as ciclopirox olamine cream and naftifine hydrochloride cream, have also proven somewhat effective against some fungal and bacterial infections. However, for many forms of onychomycosis, such as those caused by Trichophyton rubrum, T schoenleinni, T. mentagrophytes, T. sulfureum, T. verrucossum, T. interdigitalis, Epidermophyton floccosum, Microsporum audouinii, M. canis, or M. gypseum and various forms of pedis, most topical antifungal preparations have proven to be ineffective.
For deep-seated onychomycosis and pedis that have spread uncontrolled beneath the nail beds, systemic therapy is often required. One common method of systemic therapy is the administration of griseofulvin, an oral antifungal agent. However, griseofulvin has undesirable side effects such as headaches, gastrointestinal distress, photosensitivity, rashes, or leukopenia. There has been some demonstrated success utilizing topical imidazole in conjunction with oral griseofulvin to increase the cure rate, but even with simultaneous topical and systemic treatment, there are unwanted side effects associated with administration of oral antifungal agents such as griseofulvin.
In addition to causing irritation, onychomycosis and similar conditions often create damage to the nails and nail beds causing the nails to thicken, discolor, and to crack and crumble around the edges. Thus even if the onychomycosis is treated, extensive repair of the damaged nail is often required.
Topical treatments for fungal infections are particularly advantageous over systemic therapy in that topical treatments avoid the negative side effects associated with systemic drugs. However, topical antibiotic or antifungal compositions, such as nail lacquers, are often ineffective because the antibiotics cannot penetrate through the nail to which it is applied in order to reach the infected nail beds. As a result, the prior art topical treatments do not effectively deliver the antimicrobial agent to the source of the fungus or bacteria.
Conventional cosmetic nail lacquers are generally polymer-based lacquers that use nitrocellulose as a film forming agent. Modifiers such as plasticizers and resins are generally required to keep the nitrocellulose from becoming too brittle and to increase the adherence of the nitrocellulose film to the surface of the nail. Most resins used today are synthetic resins such as methacrylate and polyvinyl acetate. A common plasticizer used with nitrocellulose is tricresyl phosphate.
Thus, polymer based lacquers with antimicrobial agents have not been successful in imparting antimicrobial and antiviral agents to the nails and nail beds because nitrocellulose polymers are water insoluble, and require the use of a solvent as a carrier medium. Common solvents include ethyl acetate, amyl acetate, butyl acetate, ethyl alcohol, butyl alcohol and acetone. Butyl alcohol is most commonly used with nitrocellulose lacquers. However, these solvents often adversely interfere with the antimicrobial and antiviral agents, rendering the agents ineffective in treating fingernail and toenail infections. Solvent based lacquers are also not satisfactory because they cause the nails to dry out and also leave a brittle surface. Also, polymer based lacquers are often very viscous, and the viscosity can interfere with the delivery of the antimicrobial agent to the source of the infection which is often embedded beneath the nail.
One method of enhancing the delivery of antimicrobial and antiviral agents to the nail beds, and thereby enhancing the effectiveness of the agents, is to evulse or remove the nails prior to treatment. Prior art methods of evulsing the nails include mechanical or surgical means. There are a number of drawbacks associated with the prior art methods of evulsion, including pain to the patient, and the increased costs and time of treatment associated with the physical removal of nails.
Applicants have now discovered an effective, water-based nail lacquer that partially or completely evulses the nails, thereby enhancing the delivery of antimicrobial and antiviral agents to the nail beds, and increasing the effectiveness of topical treatment with antiviral and antimicrobial agents.
The present invention comprises a method for treating damaged and infected nails with a topical, water based nail lacquer which is applied to the nail and surrounding tissues. The method leaves a strong and durable enamel over the nail, and partially or completely evulses the nail to allow topical medication to reach the source of the infection.
The compositions of the invention provide an improved method of evulsing nails. The composition of the invention further provides improved methods for delivering antimicrobial or antiviral agents to infected nails and nail beds.